Wastewater treatment method and apparatus

ABSTRACT

Wastewater treatment operations, i.e. the coagulation, decomposition, sterilization and separation of impurities such as the sludge, organisms, etc. in a liquid to be treated are carried out by applying an AC voltage of a specific frequency between first and second electrodes provided in the liquid to be treated, and thereby making an AC field work on the same liquid. An AC voltage of a high frequency suited to the quality of the water in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the object liquid elute and an AC voltage of a low frequency are switched from one to the other in a contactless manner in a predetermined cycle, and the resultant voltage is applied to the first and second electrodes. This causes crystals and bubbles of the water to be fractionated, sludge, organisms, etc. to be fractionated, the decomposition, sterilization and separation thereof with respect to the water to be promoted, the oxidation-reduction potential and oxidation potential to be varied greatly, and the electrode self-cleaning effect by a low frequency to be produced simultaneously.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to wastewater treatment method and apparatus adapted to subject minute solid particles contained in a liquid to be treated to coagulation, separation, decomposition and sterilization. More particularly, the wastewater treatment method and apparatus according to the present invention have features which reside in treating an object liquid by greatly varying oxidation-reduction potential and oxidation potential by a field effect of a high frequency suited to each liquid to be treated and an electrochemical reaction, so as to fractionate minute solid particles in the object liquid and promote the decomposition, sterilization and separation of the fractionated particles with respect to the water.

[0003] 2. Description of the Related Art

[0004] In a method of separating and removing minute solid particles from environment contamination waste water and waste painting water, chemicals, such as a coagulant, a high molecular agent and the like have heretofore been used. The equipment for use in practicing this method has large dimensions and requires a large installation area. The equipment not only has an expensive but also takes much equipment cost for the maintenance and management thereof.

[0005] Recently, a wastewater treatment apparatus utilizing the electrolysis of water has also been proposed. Although this kind of apparatus is possible to reduce the dimensions thereof and consumes power greatly, it harmonizes excellently with the environment. In a related art wastewater treatment apparatus utilizing the electrolysis of water, an AC voltage of a low frequency of around 30 H_(Z)-80 KH_(Z) is applied to electrodes. This apparatus does not have a satisfactory performance of fractionating crystals of water and occurrence of electrode becoming dirty, fractionating minute solid particles, promoting a particle separating effect with respect to the water, and, especially, treating a large quantity of water.

SUMMARY OF THE INVENTION

[0006] The present invention has been made in view of the above-mentioned circumstances, and provides wastewater treating method and apparatus adapted to easily treat water the quantity of which is as large as around ten times reaction that of the water treated by a related art method and apparatus of this kind, by generating an electrochemical reaction in object water by fractionating minute solid particles and the like by not using chemicals, improving a particle decomposing, sterilizing and separating effect promoting performance with respect to the water, and thereby greatly varying the oxidation-reduction potential and oxidation potential; and suppress an equipment installation area to a minimum level and running cost.

[0007] In the wastewater treatment method, in which impurities, such as sludge, organisms, etc. in a liquid to be treated are coagulated, decomposed, sterilized and separated by applying an AC voltage of a predetermined frequency between a first electrode and a second electrode provided in the object water, and thereby making an AC field work on the same water, the frequency of the AC voltage used is set to a high level suited to the quality of the water, in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in AC electrolysis of the object liquid elute.

[0008] The method preferably has the following constitution.

[0009] (1) When the liquid to be treated is underground water, a frequency in the vicinity of 310 KHz is used.

[0010] (2) When the liquid to be treated is city water, a frequency in the vicinity of 170 KHz is used.

[0011] (3) A third electrode is provided in a non-connected state in the liquid to be treated.

[0012] (4) The first and second electrodes are self-cleaned by using a low frequency in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the object liquid elute.

[0013] (5) An AC voltage of a high frequency for making an AC field work on the object liquid and an AC voltage of a low frequency for self-cleaning the first and second electrodes are switched from one to the other in a contactless manner in a predetermined cycle, and the resultant AC voltage is applied to the electrodes.

[0014] The wastewater treatment apparatus adapted to subject impurities, such as sludge, organisms, etc. in a liquid to be treated, to coagulation, decomposition, sterilization and separation by applying an AC voltage of a predetermined frequency between a first electrode and a second electrode provided in the liquid to be treated, and thereby making an AC field work on the same liquid, the apparatus including an AC power source for generating an AC voltage set to a predetermined frequency, and a control unit for applying between the first and second electrodes an AC voltage of a high frequency suited to the quality of the water, in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the object liquid elute, the apparatus being formed so as to fractionate the impurities by applying an AC field generated by the AC voltage of a high frequency to the object liquid, and thereby promote an efficient separation of the fractionated impurities from the water.

[0015] The apparatus preferably has the following structures.

[0016] (1) The control unit applies an AC voltage of a high frequency which promotes the separation of the impurities from an object liquid by making an AC field work on the same liquid and thereby fractionating the impurities, and which is in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the object liquid elute, and an AC voltage of a low frequency for self-cleaning the first and second electrodes to the same electrodes.

[0017] (2) The control unit switches an AC voltage of a high frequency and an AC voltage of a low frequency from one to the other in a contactless manner in a predetermined cycle, and applies the resultant AC voltage to the above-mentioned electrodes.

[0018] (3) The first and second electrodes are formed of multiple, coaxial pipe type electrodes.

[0019] (4) A third electrode is provided in a non-connected state in the liquid to be treated.

[0020] According to the present invention, the use of a high frequency suited to the quality of the water, in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the liquid to be treated elute, causes crystals and bubbles of water to be fractionated, sludge, organisms, etc. to be fractionated, the production of water decomposing, sterilizing and separating effects to be promoted, the oxidation-reduction potential and oxidation potential to be varied greatly, an electric field effect (vibration effect) based on the high frequency suited to the quality of the water to increase, and a water sterilizing effect to be thereby produced. Especially, when city water, underground water, etc. are used as drinking water and food manufacturing water, the safety thereof can be improved by sterilizing the same. In a sewage treatment, the sterilization thereof, the decomposition of chlorine compound and dioxin, COD(chemical oxygen demand) and the separation and decomposition of environment contaminating substances have enabled the prevention of river contamination and the recycling of sewage.

[0021] Since the self-cleaning of the electrodes is done by using a low frequency, the substances deposited thereon are removed therefrom, and the surface of electrodes are regenerated, this enabling a water treatment efficiency to be heightened.

[0022] Since a third electrode is provided in a non-connected state, the elution of the metal ions is further promoted, and the oxidation-reduction potential and oxidation potential are varied greatly.

[0023] Multiple coaxial pipe type electrodes are used as the first and second electrodes, therefore an aqueous solution having a low electrical conductivity can be electrolyzed with a high efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a block diagram of an electric circuit of the wastewater treatment apparatus according to the present invention;

[0025]FIG. 2 is a diagram showing the relation between oxidation-reduction potential and oxidation potential and frequencies;

[0026]FIG. 3 is a block diagram of an electric circuit of another embodiment;

[0027]FIG. 4 is a diagram showing an electrode structure of double pipes; and

[0028]FIG. 5 is a diagram showing modified examples of multiple, coaxial pipe type electrodes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram of an electric circuit of the wastewater treatment apparatus according to the present invention. In a treatment vessel 1, a liquid 2 to be treated, such as environment contamination waste water and the like is placed, and a first electrode 3 and a second electrode 4 are inserted. The first and second electrodes 3, 4 are connected to output terminals 11, 12 of a frequency variable type AC power source 10. From the AC power source 10, an output, for example, 1 KW, of a variable frequency of several Hz to 1 MHz suitable for the electrolysis of the object liquid is obtained. The AC power source 10 includes a frequency generating circuit (OSC) 13, a switching circuit (SW) 14 for switching frequencies from one to the other in a predetermined cycle, and a power amplifier circuit formed of a first power amplifier circuit member (P. A.) 15 and a second power amplifier circuit member (P. A.) 16.

[0030] The switching circuit 14 constitutes a control unit adapted to carry out a switching control operation for switching from one to the other in a contactless manner in a predetermined cycle an AC voltage of a high frequency which makes an AC field work on the liquid to be treated, fractionates impurities and promotes the separation, decomposition and sterilization of the resultant impurities with respect to the water, and which is in a frequency band in which an electrochemical reaction is generated with metal ions eluting in the AC electrolysis of the object liquid, and an AC voltage of a low frequency for self-cleaning a first electrode 3 and a second electrode 4.

[0031] The second power amplifier circuit member 16 is connected to the output terminals 11, 12, and an AC power of a predetermined frequency and a predetermined output level is supplied between the first and second electrodes 3, 4 via these output terminals. The current and voltage supplied to the electrodes 3, 4 can be ascertained in an ammeter A and a voltmeter V respectively.

[0032]FIG. 2 shows the relation between oxidation-reduction potential and oxidation potential and frequencies. The maximum variation values of the oxidation-reduction potential and oxidation potential are shown between two points of specific frequencies F₁ and F₂, and an ionization effect and electrochemical reaction effect appears noticeably. A low frequency F_(L) is suitable for the self-cleaning of the electrodes, and has an effect in greatly varying the oxidation-reduction potential and oxidation potential while self-cleaning the electrodes. A high frequency F_(H) generates fine bubbles, and has a large field effect. A high frequency also has an effect in greatly varying the oxidation-reduction potential and oxidation potential by fractionating crystals of water, fractionating sludge, organisms, etc. and promoting the effect in decomposing, sterilizing and separating the fractionated substances with respect to the water. It was ascertained that the relation between the quantity of generated hydrogen and frequency was qualitatively identical with that between the ORP and frequency.

[0033] The frequencies F_(L), F_(H) of various kinds of liquids to be treated are as follows. F_(L) (Hz) F_(H) (KHz) Underground water 10 310 City water 70 170 Paint treatment liquid 30 210 Unused deep frying oil x 62 Oxidized deep frying oil x 17

[0034] Since the frequencies at which the cleaning effect and field effect are produced thus differ depending upon the kind of liquids to be treated, an optimum wastewater treatment apparatus for these liquids to be treated is necessarily designed.

[0035] Another embodiment of the present invention will now be described. FIG. 3 is a block diagram of an electric circuit of this embodiment. In this embodiment, third electrodes are added to first and second electrodes, and the construction of the remaining portion of the embodiment is identical with that of the corresponding portion of the previously-described embodiment. An electrode structure includes a first electrode 3, a second electrode 4 and third electrodes 5, and the third electrodes 5 are merely submerged in a liquid in which the first and second electrodes 3, 4 are placed, i.e. the third electrodes are provided in a non-connected state. When an Al/Mg electrode and a titanium electrode are used as the first electrode 3 and second electrode 4 respectively in, for example, an apparatus for treating environment contamination waste water, Al/Mg electrodes identical with the first electrode 3 are used as the third electrodes 5. When an electric current is supplied to the first and second electrodes 3, 4, the third electrodes are melted to generate hydrogen even if an electric current is not supplied to the third electrode 5. As a result, it was ascertained that the oxidation-reduction potential and oxidation potential were varied greatly to cause the water treatment efficiency to increase by 30%.

[0036] The electrodes used are plate type electrodes, or single or multiple, coaxial pipe type electrodes, and the metals of which the electrodes are to be made can be selected among various kinds of metals depending upon the kind of water to be treated. The properties of metal ions and electric chemical reaction of, for example, titanium, platinum, palladium, iridium, carbon, aluminum, magnesium, zinc, copper, silver, etc. are utilized. FIG. 4 shows an electrode structure of double pipes, and each double pipe electrode includes an inner pipe 6 and an outer pipe 7. These pipe electrodes have a large area of opposed surfaces, and can reduce the impedance to a low level. In the example of FIG. 4, plural double pipe electrodes are parallel-connected to form a structure adapted to further reduce the impedance.

[0037]FIG. 5 shows modified examples of multiple, coaxial pipe type electrodes. Various types of coaxial pipe type electrodes including a triple, coaxial pipe type electrode (FIG. 5A), a quadruple, coaxial pipetype electrode (FIG. 5C) and a quintuple, coaxial pipe type electrode (FIG. 5d) can be formed simply by varying the diameter of the pipes. Using such multiple, coaxial pipe type electrodes is specially effective for treating an aqueous solution of a low electric conductivity, for example, an oil, pure water, superpure water, etc., and enables the electrolysis of an aqueous solution of a low temperature to be conducted efficiently.

[0038] Copper, silver, platinum, zinc, aluminum, magnesium, titanium, etc. can preferably be selected as materials for the coaxial pipe type electrodes. 

What is claimed is:
 1. A wastewater treatment method adapted to subject a liquid to be treated to the coagulation, decomposition, sterilization and separation of impurities such as sludge, organisms, etc. by applying an AC voltage of a predetermined frequency between a first electrode and a second electrode provided in the liquid to be treated, and thereby making an AC field work on the object liquid, comprising the step of: using a high frequency suited to the quality of the water and in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the object liquid elute as the frequency of the AC voltage, and an electrochemical reaction.
 2. A wastewater treatment method according to claim 1, wherein, when the liquid to be treated is underground water, a frequency in the vicinity of 310 KHz is used.
 3. A wastewater treatment method according to claim 1, wherein, when the liquid to be treated is city water, a frequency in the vicinity of 170 KHz is used.
 4. A wastewater treatment method according to claim 1, wherein a third electrode is provided in a non-connected state in the liquid to be treated.
 5. A wastewater treatment method according to claim 1, wherein the first electrode and second electrode are self-cleaned by using a low frequency in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the liquid to be treated elute.
 6. A wastewater treatment method according to claim 5, wherein an AC voltage of a high frequency for making an AC field work on the liquid to be treated, and an AC voltage of a low frequency for self-cleaning the first and second electrodes are switched from one to the other in a predetermined cycle, the resultant AC voltage being applied between the first and second electrodes.
 7. A wastewater treatment apparatus adapted to subject a liquid to be treated to the coagulation, decomposition, sterilization and separation of impurities such as sludge, organisms, etc. by applying an AC voltage of a predetermined frequency between a first electrode and a second electrode provided in the liquid to be treated, and thereby making an AC field work on the object liquid, comprising: an AC power source for generating an AC voltage set in accordance with the predetermined frequency, and a control unit for applying between the first and second electrodes an AC voltage of a high frequency suited to the quality of the water and in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the object liquid elute, an AC field based on the AC voltage of a high frequency being applied to the object liquid to thereby fractionate impurities and promote the decomposition, sterilization and separation of the resultant impurities with respect to the water.
 8. A wastewater treatment apparatus according to claim 7, wherein, when the liquid to be treated is underground water, a frequency in the vicinity of 310 KHz is used.
 9. A wastewater treatment apparatus according to claim 7, wherein, when the liquid to be treated is city water, a frequency in the vicinity of 170 KHz is used.
 10. A wastewater treatment apparatus according to claim 7, wherein the first and second electrodes are formed of multiple, coaxial pipe type electrodes.
 11. A wastewater treatment apparatus according to claim 7, wherein a third electrode is provided in a non-connected state in the liquid to be treated.
 12. A wastewater treatment apparatus according to claim 7, wherein the control unit is adapted to apply to the first and second electrodes an AC voltage of a high frequency which makes an AC field work on the object liquid, fractionates impurities and promotes the separation of the resultant impurities from the water, and which is in a frequency band in which metal ions, hydrogen, oxygen is dissolved into and take out in large quantities, occurring in the AC electrolysis of the object liquid elute, and an AC voltage of a low frequency for self-cleaning the first and second electrodes.
 13. A wastewater treatment apparatus according to claim 12, wherein the control unit switches an AC voltage of a high frequency and an AC voltage of a low frequency from one to the other in a predetermined cycle, and applies the resultant AC voltage between the first and second electrodes. 